Fond des Vaulx

Fond des Vaulx is a small, wild karst valley tucked just a few minutes from the centre of Marche-en-Famenne, in the province of Luxembourg, Wallonia. Covering roughly 15 hectares, the valley stands in sharp contrast to the flat farmland plain surrounding the town — descend into it, and the landscape shifts abruptly into a rugged world of rock, caves and woodland.

What makes it geologically special?

The valley sits on the Calestienne, a limestone band running across southern Belgium. Over millions of years, acidic water flowing down from the Ardennes massif met the limestone bedrock and carved out an intricate network of caves, sinkholes and fissures. This slow erosion produced the jagged terrain that defines Fond des Vaulx today. Because of its geological importance, the site is part of the Famenne-Ardenne Geopark, Belgium's first UNESCO Global Geopark.

What can visitors see there?

The valley's best-known feature is the Trotti aux Fosses, a deep, funnel-shaped chasm considered unique in Belgium and protected as a cavity of scientific interest. Along the walking trails, visitors also pass several caves, including the Grotte de la Ducasse and the Trou du Renard, as well as steep rock walls and other karst formations that have long fed local legends about this mysterious corner of the region.

Getting there and trail options

Access to the valley runs through a long tunnel beneath the Liège–Jemelle railway line, giving the walk an unusual, almost cinematic start. Once inside, three marked trails ranging from 2.2 to 4.4 km let visitors explore the area at different levels of effort and available time. Fitness enthusiasts can also use a Hébert-style obstacle course set up in the valley, while a covered barbecue area offers a spot to rest for families and groups partway through the walk.

Nature and species protection

Beyond its scenery, Fond des Vaulx is a valuable nature reserve. The site is part of the Life Hélianthème project, which works to restore limestone grasslands — one of the richest and most threatened ecosystems in Wallonia. The valley's particular microclimate and varied limestone substrate support numerous plant species typical of calcareous habitats that are otherwise uncommon elsewhere in the region.

Frequently asked questions

How long does it take to visit Fond des Vaulx? Depending on the trail chosen, a walk takes roughly 45 minutes to just under two hours — the shortest loop is 2.2 km and the longest 4.4 km.

Is entry to the site free? Yes, the valley is an open-access walking area with no entrance fee.

Can visitors explore the caves on their own? The trails run alongside cave entrances and rock formations, but entering the caves themselves is not the main purpose of a visit — this is primarily a scenic and nature walk rather than a caving destination.

Who is this site best suited for? Fond des Vaulx works equally well as an easy family outing with a barbecue stop or as a longer excursion for geology and nature enthusiasts looking for a lesser-known highlight of the Famenne-Ardenne region.

How far is it from central Marche-en-Famenne? The entrance to the valley lies just a few minutes on foot or by car from the town centre, making it an easily accessible attraction even for a short visit.